1. Field of the Invention
This invention relates to flexible intumescent compositions suitable for use as firestops in deterring the spread of fire, smoke, and fumes as may happen during a fire in a building.
2. Related Art
Fire, smoke, and fumes in confined spaces, such as multi-floor buildings, can be extremely life threatening. Frequently, if fire originates in the space between a floor and ceiling of such a structure, the fire, and resultant smoke and fumes, will tend to spread to other open spaces in the building, especially to open spaces above the point of origin of the fire.
The spaces between conduits, piping, and the like, and the floors and ceilings through which they pass are known as "through-penetrations." If not protected by fire resistant materials, a through-penetration offers an area of low resistance to fire, smoke and fumes, and in essence may serve as a chimney for heat, flame and fumes. Through penetrations may be filled with commercially available fire retardant and intumescent putties, caulks, wraps, sheets, or mats, known in the art as "firestops."
Representative firestop products are disclosed in product brochure number 98-0701-3508-6 (published 1990) from Minnesota Mining and Manufacturing Company (3M). The 3M products are currently known under the trade designations "CP 25WB" "CP 25 N/S" "CP 25 S/L" and "Firedam" (caulks); "MPP-4S" and "MPS-2" (moldable putties); and "FS-195" (wrap/strip) and "CS-195" (metal reinforced sheet). These products are variously described in assignee's U.S. Pat. Nos. 4,273,879, 4,364,210, 4,467,577, and 4,952,615. Other intumescent fire retardant materials have been used, such as those known under the trade designations "Palusol" (commercially available from BASF) and "Expantrol" (commercially available from 3M Co.), the latter being an alkali metal silicate.
These firestop products and others have been widely used for reducing or eliminating the chimney effect for through-penetrations and pass the rigorous American Society of Testing Materials (ASTM) fire endurance test (ASTM E-814) after intumescing and charring wherein the material is not easily blown out of penetrations when subjected to water hose pressure such as may be present during fire fighting. Therefore, essential characteristics of a firestop material include the ability to expand and to char, and for the charred material to have sufficient strength to withstand the test requirements.
In spite of the above compositions, there exists a need in the art for a firestop composition which retains its expansion, low compression set, and flexibility after long-term exposure to oxidative environments.